Патент USA US2407287код для вставки
SepìII E0, i946, E. LABIN EAW/,287 COURSE BEACON F‘i‘led June 28, 1941 2 Sheets-Sheet l _________‘_.________________________.________.__._;_.;_| .4 Tl. m r laH à p n» _ _c nk sr „m A r f r W ME ff tn „ml L_vßllL”_ «.l„aAß F. ?v , A ,___ ,5 i Fles. BY l ATTORNEY sep@ my ma E. LABIN 2,407,2@7 ' COURSE BEACON -Filed June 28, 1941 2 Sheets-Sheet 2 Patented Sept. l0, 1946 2,407,287 unirse srarss PATENT oFricE 2,407,287 COURSE BEACON Emile Labin, New York, N. Y., assignor to Federal Telephone & Radio Corporation, a corporation of Delaware Application June 28, 1941, Serial No. 400,259 14 Claims. (Cl. 250-11) l 2 This invention relates to radio direction-indi cating and direction-finding apparatus, and is directed particularly to means for producing an aircraft iiight beam of high accuracy. It is an object of the invention to provide means undetectable by the enemy, hence, relatively secret. A pair of such beacons could be projected thus very accurately define this desired location, for producing an airplane course beacon of greater directive accuracy and longer range than which, say, it is desired to bomb. In order to assure further secrecy these beacons could be from spaced points within one territory to inter sect at a desired location in another territory and varied while the bombers are en route to their has hitherto been attainable. objective, and their intersection need only be Another object is to provide an improved radio beacon which will not give distorted and mislead 10 made to occur at the objective as the bombers are immediately approaching. It would thus be ing course information due to the presence of re fleeting objects. possible to bomb a ñxed target with relative accu racy without requiring bombardiers to first see A further object is to provide improved means their targets. ' for varying the directivity of an airplane course In order to obtain increased accurate course beacon at will. 15 range I propose to use pulse modulation trans It is also an object to provide an improved mission means in which a series of impulses of course beacon that does not depend upon antenna unusually high instantaneous power is trans directivity for its accuracy. mitted. To establish a course two transmitting Other objects and various further features of novelty and invention will hereinafter be pointed 20 antennas are each fed with energy of the same out or will become apparent from a reading of the impulse frequency following specification in conjunction with the drawings included herewith. In said drawings Fig. 1 shows schematically a preferred arrange ment and layout of transmitting and receiving 25 but displaced a certain interval of time bo, one series with respect to the other. Along any line apparatus in accordance with features of the invention; extending radially outwardly from the midpoint between these antennas the time interval between Fig. 2 is a graphical representation of energy receivable pulses will be the same, and thus concharacteristics at diiierent positions in the layout of Fig. 1; 30 stant, along that line or course. Now, if an airplane carries receiving equipment Figs. 3 and 4 are graphs illustrative of the op responsive to the time displacement between suc eration of the arrangement shown in Fig. 1; and cessive impulses of both these series, it can be Fig. 5 shows geometrical considerations involved given an indication of any course to be followed; in my novel course system. The invention is concerned with improved 35 that is, the course may be determined by this time interval. I consider it preferable, however, to pro directing apparatus for indicating to an airplane vide the receiving Sets responsive only to one pre pilot a desired direction of flight with high accu determined time interval and then to control the I‘äCY. time interval between pulses of both transmitting This novel system contemplates a directive ar rangement whereby angular directive accuracy 40 sources by appropriate phase adjusting means in order to send the aircraft out on a fixed direct, or improves with distance from the transmitter and controlled indirect course. a beam may be projected for distances hitherto With this brief general introduction, the inven unobtainable with accuracy. The system is at tion> will now be described in connection with the the same time further adaptable to changes in directivity. 45 drawings. Fig. 1 schematically shows in block diagram form elements of my novel beacon sys Such a system will be appreciated as having tem, including the transmission and receiving very deñnite civil as well as military value. In (airplane) stations. In the form shown the commercial aviation there is a deiinite call for a transmitting equipment includes a pair of an course beacon having great accuracy and substan tennas lil and II spaced preferably a substantial tially unaiîected by large reflecting bodies, such as distance apart for greater accuracy, as will be clear. Antenna Il) is associated with transmitter A, and antenna Il with transmitter B. Each of these transmitters is supplied with a periodically that may be readily followed and that is relatively 55 recurrent impulse signal spaced in time, one with high mountains. The present invention will help to ñll such needs. From a military point of View it is considered desirable to provide a sharply directive beacon 2,407,287 3 4 respect to the other. In a preferred form a single no matter what the form of the impulses just impulse generator l2 is employed for supplying both transmitters, and in substantially the follow ing manner. Generator l2 supplies impulse energy directly to transmitter B. A receiving antenna lli’ at station A is receptive to this im pulse energy; and, after receiving the pulses in receiver S and appropriately delaying the same as long as they are short enough'. From the Fourier formula the amplitude Am for the mth harmonic of a single series of the transmitted pulses over the period T is given as_ by time-delay means i3, the impulses are re where f(t) represents the pulse shape. A „f-TL -2 Tf(t) transmitted at A. A pulse displace indicator 2| (l) Now, since',f(t)=0 for values of t between d and T, the integral is limited by tzal. However, if d is so small that for all reasonably small values receives energy from the receiver 8 and from the output of delay means i3 for comparison indi cation, whereby the eiiect of the time delay means i3 can be observed and monitored. cos mot. d t of m If desired, a cos mwd=l receiver and monitoringr circuit 9 may also be provided at B for ascertaining whether the delay it is found that for all forms of f(t) if Vm is rea between transmitted impulses from A and B are spaced properly to denne a correct course. sonably small low, along any radial direction from the mid.. 2 T 2 a point between A and B, and particularly at 20 greater distances, received impulse energy will that is, for all impulse forms the amplitude of comprise a recurrent pattern of two pulses, spaced the lower harmonics is equal `to the mean value in time according to the radial direction. Since of the periodic function fût). Thus for a single any such pulse pattern will have a definite har monic make up, I propose to employ harmonic 25 series of pulses all low harmonics have the same analysis the receiver to give the course indi amplitude. cation to the pilot. Accordingly, a preferred form In the case of a double pulse series, however, the different low harmonics will have diiîcrent of receiver comprises radio and intermediate fre amplitudes. The amplitudes of the various har quency stages it, and limiting and detecting means, l5 and iS, respectively, After detection 30 monics forming the received complex double pulse series will vary simply as cos mwb. This will be of the two-pulse signal, for purposes that will clear by considering one series of pulses, say later become apparent, I propose to identify by appropriate ñlter means il, I8, le, and 2Q various from A, as» odd-harmonics of the signal in addition to the Am--Q-,L f(t).cos mwtdt-îfûfuydt fAo) :EAW @es mwa fundamental and an even harmonic. Informa tion acquired from a dii'îerential indication of various voltage outputs of these ñlters may give a direct indication as to whether the desired course (2) (s) and the other, say from B, as fßw =ZA,„. COS mwc- b) <4) is being followed. Fig. 2 shows schematically the energy output 40 The combined result of these signals, represent of the respective transmitters and the kind of ing received energy will be energy received at the craft that is being guided. Pulses of the same period T are transmitted at b QU) :ZZAW 00S mgb' A and B and are time-displaced from each other, as so adjusted by the phasing control I3. In transmission from A to the receiver there will cos mw t-î (5) Since the term 2Am is clearly not dependent on the value of b, and since the term be a certain delay TA, and another delay rs as sociated with energy coming from B. If the in terval between the radiation of a pulse from cos mw (il) 2 A and the radiation of the corresponding pulse 50 from B is bu, the -total displacement between will vary periodically between +1 and -1 n0 pulses at the receiver will be b, the resultant of matter what value is chosen for b it is clear that controlled and transmission delays-bo-rA-l-TB. the term cos (l/gmwb) is the sole term deñning We shall new analyze the received signal, two the relation of the absolute magnitude of the pulses displaced by an interval b. received energy for any harmonic to the dis» It may be shown from a harmonic analysis placement b between pulses. of the received signal g<t> that all frequencies Fig. 3 is a series of graphical representations showing how the magnitude Ym of this which are multiples of 60 will have phase and amplitude characteristics dependent upon the delay of one series with re~ spect to the other, that is, upon the magnitude of b. The phase variation may be neglected since the detected harmonics are used only to give currents proportional to the magnitude oi their amplitudes. Furthermore, since only lower order harmonics are to be considered, it will be assumed that the duration d of the impulses is small enough for the amplitude of the Various harmonics of each series to be independent of the harmonic order. As will be shown in the csmwb o 2 term varies for a number of the lower order h'armonies when b is considered for Values of zero to T 2 It will be observed that all of the odd-order har monic curves intersect and are thus equal for a delay b of T following paragraph, this assumption is valid 75 between received impulses. Those odd harmonics 5 2,467,287 6 of the orders 4m-l-1 (m being zero or any whole number) will vary with b about indications for more courses than the true one T 4 In order to eliminate the error of following a false course I propose to employ some additional indication of the value of an even harmonic, say as a cosine function varies about the second, which passes through zero only at 4 T , b-r that is, with a negative slope; and the odd har 10 monies of orders 4m-l-3 will vary with b about , Thus, by simultaneously following the second T 4 harmonic zero and a zero of one of the §-Curves' a pilot will be “on course.” ItA will further be observed in connection with as a sine function varies about 15 Fig. 4 that differential curves for higher order harmonics (e. g. §35) are of steeper slope at 4 T that is, with a positive slope. It will be seen, 4 then, that two odd harmonics of successive order than lower harmonics. This steeper slope may 20 may be used to define an axis about be utilized as the correct course is approached to T give higher magnitude indications in the “on 4 course” neighborhood of In accordance with features of my invention I b: Z 4 use two such successive harmonics to obtain a 25 and thus to follow the course still more accu differential indication of their relative magni rately. On the other hand, when considerably tudes. “off course,” it may be desirable to employ lower In Fig. 4 I show graphically the resultant curves obtained from differential Superpositions of such order harmonic differentials (e. g. §31) to elimi 30 nate false zeros and to be able to follow down successive odd harmonics of the received signal only one slope to get "on course.” It thus ap pattern. In this figure, curve §31 represents a pears preferable toy use the §31 and quantity proportional to the diiïerence between the third harmonic and the fundamental, and §35 the third and fifth' harmonic differential. An indications when the receiver plane is far from even harmonic, in the present instance the sec the axis, and §35 or §51 when in the neighborhood ond Y2, is also shown, as it is employed for pur of the axis. If b is permitted to vary only within poses that will be later pointed out. relatively small, limits about Y. It will be noted in connection with the curves ' ` l' of Fig. 4 that both the differential curves vary in the same sense either side of a norm, where 40 4 then the §31 curve may be employed merely for b quadrant identification purposes. Since the maximum variations of b about When time-displacement b of received impulse 45 vT patterns is greater than 4 T 4 (when bo has the value ë) odd-harmonic differential energy will have posi 50 are determined by D, _the transmission time be tween A and B, variation in b may readily be kept tive values; and when these differentials are less do-wn to a small fraction of T by appropriately than selecting the pulse period T sufficiently large 4 resultant energy is negative. It thus appears with respect to the distance between transmitters 55 A and B. Referring to the elementary diagram of Fig. 5, I show the geometrical considerations involved in rotating the direction of the course that if a flight course be determined by a differ ence b between pulses equal to T 4 a receiver adapted to ñlter out harmonics and compare differentials as above-indicated will have zero output whenever the receiver is exactly 60 without physically displacing antennas I0 and l l. Assuming for the moment that bo is 4 “on course.” Drift to one side will give rise t0 65 too large a differential with resultant positive it is clear that unless the receiver is “on course,” §-output, and the converse will hold for drift the detected pulse time displacement b will not be “off course” in the opposite sense. T Of the many indicating means that will sug 4 gest themselves to the reader, I prefer to employ 70 a voltmeter giving visual indication of positive but rather some other value equal to or negative harmonic differential voltage values. In a practical application of this indication sys tem it will be seen that by using only the y or differentia1 curves, it is possible to obtain zero 75 (r being the differential ril-rs, see Fig. 2).A ' moms? 8 7 Now, if a designates the angle of OM (i. e. a line joining some point between transmitters A and B to the receiver) measured clockwise from the reference line XOX’ (perpendicular to a line between transmitters A and B) then for values of the distance OM very much greater than the distance AB, sin OC: T error in the B sector and 0.40o in the A quadrant. Although I have described my invention in connection Iwith the preferred forms illustrated, it is to be understood, of course, that many modi fications will fall within its scope. For example, if it should be deemed inexpedient to provide the impulse generator l2 feeding both transmitters A and B by the method shown, a transmission line arrangement could be employed. In this D 10 case generator i2 could feed both transmitters where D as above-indicated is the transmission A and B, simultaneously and directly. The above time between A and B. A condition precedent to described delay means could then be provided in being “on course” is that bo, the delay instituted the transmission line intermediate the pulse gen at the transmitters by the delay means I3, plus erator and one of the transmitting stations. A the transmission delay r be equal to 15 monitoring circuit also similar to the one above described could be employed for the same 'stand T ardizing purposes by disposing it so as to com 4 pare the delay between impulse energy fed to In order, then, to denne a bo that will produce both transmitters. or set up a course at a desired angle an with the It is further clear that the invention is not to perpendicular XOX’ be considered limited to the particular order har monics described. For example, higher odd har T monics than the iifth may be employed for even Tho In other words, to rotate the direction axis an ' angle an clockwise from the perpendicular, the time between pulses at the transmitter must be greater course accuracy inasmuch as the higher the harmonic order the closer a t peak ap proaches the true course, and the steeper this y curve’s slope at b: l" 4 30 Although other even harmonics may be employed To this end, the delay means i3 may be used for the true-course check as above indicated, it to control bo and appropriate monitoring and is preferred that the second be employed, for this indicating means 2l provided for accurately ob harmonic has the property of only reaching Zero serving and. Calibrating course directivity. For once in the entire interval from purposes of easier calculation and design I prefer to employ a spacing between stations A and B b=0 to b=g such that the interstation delay D will be some integral sub multiple of the interval Ii a limiter of known construction is employed in conjunction with received energy only the T 40 stronger signals, i. e. the impulse energy, will be 4 eñective as to the rest of the receiver. In this Since the variation in r incurred in rotating way it Will be possibile to eliminate Very substan the course axis from OA to OB (i. e. from a posi tially any reflection or other disturbing eiïects tion 90° on one side of XOX’ to a position 90° due to terrain irregularities, as will be clear. on the otherv side of XOX’) is 2D, the minimum 45 Furthermore, since the maximum amount of the value of impulse displacement that need be used in ac cordance Iwith the invention is within T 4 T 2 is determined by 2D. Thus The signal-to-noise ratio in the receiver may T further be increased by half-wave rectifying should equal at least 8 for complete rotation of the course (180°). When the course coincides with XOX’, i. e. when the delay some of the output energy, say from the funda mental filter l?, and employing this rectiiìed en ergy appropriately to control a blocking signal, as more fully disclosed in my copending U. S. ap plication Serial No. 385,282, ñled April 1, 1941. It is further to vbe observed that in addition to the peak-to-zero amplitude variation of §35 repre sents approximately a fifth of the interval T presenting advantages inherent in pulse modu lation, my novel directing system does not re quire that antennas i0 and H be of any par ticular directive nature. It is preferable that 4 they be of the same general form and charac ter so as each to propagate in substantially the in the B or right-hand quadrant, corresponding to about 23° course variation in this sense. In 65 same manner, but they need not be of the di rective type. If they are non-directive, it is clear the A or left-hand quadrantl this amplitude vari that courses of the same strength may readily ation corresponds to a b decrement of a third be set up in any desired direction without hav of the ing to make any physical adjustments or alter T 70 ations in the antennas. A mere single manual 4 adjustment of the delay means I3 is all that is interval-representing 40° angular displacement needed. that average precision for a 1% indication varia t is also to be noted that although I have de scribed an arrangement in which course control tion in the §35 readings will represent 0.23o course is eiîecterli at the transmitting end, means may in that quadrant. It would appear, therefore, 2,407,287 9 10 be provided whereby the pilot can set his own course for any given relation of transmitted im pulses. It is clear that to this end time delay means effective to displace received impulses of a double-pulse signal with respect to each other may be provided at the receiver, and this phase delay means may be adju-stable by the pilot. In tiple frequencies for indicating a characteristic of the received impulse energy. this way if a single course were deiined by a 5. In a course beacon system, a receiver accord ing to claim 4, in which said indicating means includes means supplying the effective energy of said two frequencies in opposition and means indicating the resultant eiîective energy. 6. In a course beacon system, a receiver includ ing means for receiving impulse energy, iilter could set his course at will with respect to the l0 means responsive to received impulse energy, said given pulse interval at the transmitters, a pilot fixed course by a mere manual adjustment of his phase control means. Alternately, in what would seem a far simpler arrangement, appropriate adjustable phase dis placement network means could ybe provided in the output circuits of certain filters l1, i8, IS. and 20. Calibrated adjustment of the phase of one odd-multiple frequency with that of another would serve to displace the b value at which a g' or differential curve would have zero magnitude, and hence enable a pilot to set his own course with respect to a standard transmitted impulse interval. The pilot could thus obtain readings exactly as described in the foregoing and follow his course as easily. filter means comprising means for singling out the fundamental, third, and ñfth harmonics of the impulsing frequency of said received energy, and indicating means responsive to Said singled out frequency energy, said indicating means in cluding means supplying the effective energy of two of said frequencies in opposition and means indicating the resultant effective energy. 7. In a course beacon system, a receiver accord ing to claim 3, in which said ñlter means further comprises means singling out energy of an even - harmonic of the impulsing frequency of said re ceived energy, and means indicating the effective value of said even harmonic energy. 8. In a course beacon system, a receiver accord ing to claim 3, in which said iilter means further comprises means singling out energy of the sec It might be mentioned with regard to the lat ter forms of the invention that they are partic ond harmonic of the impulsing frequency of said ularly adaptable when it is desired to send a number of bomber squadrons out on their mis received energy, and means indicating the eiïec sions simultaneously. Each pilot would then be 30 tive value of said second harmonic energy. able to set his own course with respect to the 9. A course beacon system comprising a pair beacon which may be used by all pilots. of spaced antenna means, means supplying each What is claimed is: of said antenna means with impulse energy of l. The method of guiding a mobile unit by sig the same impulsing frequency, phase delay means nals from a plurality of fixed spaced antennas 35 intermediate said supplying means and at least which comprises generating energy in a periodi one of said antenna means, whereby impulse cally recurrent series of relatively short impulses, energy emitted by one of said antenna means is dividing such energy into a plurality of similar phase displaced with respect to impulse energy portions, introducing a relative delay between emitted by the other of said antenna means, and corresponding impulses in said portions, trans 40 receiver means responsive simultaneously to mitting from each of said antennas energy from energy emitted by both said antenna means, said one of said portions, simultaneously receiving receiver means including filter means responsiveY to received impulse energy and singling out fre energy radiated by each of said antennas, filter quencies that are odd multiples of said impulsing ing said received energy into individual odd frequency and indicating means responsive to multiple frequencies of said periodical recurrence, two of said odd-multiple frequencies for indicat and obtaining an indication of the relative mag ing a characteristic of the received impulse nitudes of the energy of two of said odd-multiple energy, whereby a course indication may be frequencies. obtained. 2. The method of guiding a mobile unit which 10. A course beacon system comprising means comprises transmitting from a pair of spaced 50 for transmitting from a ñrst fixed point energy points energy in a periodically recurrent series in a periodically recurrent series of relatively of relatively short impulses, phase-displacing short impulses, means for transmitting from a impulse energy transmitted from one of said second point spaced from said ñrst point similar spaced points with respect to impulse energy transmitted from the other of said spaced points, 55 impulse energy phase-displaced with respect to energy transmitted from said first point, means simultaneously receiving energy radiated from for simultaneously receiving energy radiated each of said spaced points, filtering said received from each of said points, and means for obtain energy into individual odd-multiple frequencies ing an indication of the relative magnitudes of of said periodical recurrence, and obtaining an indication of the relative magnitudes of the 60 the energy of two frequency components of said received impulse energy, said components being energy of two of said odd-multiple frequencies. odd multiples of said periodic recurrence. 3. In a course beacon system, a receiver includ 11. In a course beacon system, impulse generat ing means for receiving impulse energy, filter ing means, a pair of spaced antennas, phase de means responsive to received impulse energy for lay means responsive to energy from said impulse singling out individual odd-harmonic components generating means, means supplying energy from of the impulse frequency, and indicating means said impulse generating means to one of said an responsive to two of said odd-harmonic compo nents for indicating a characteristic of the re tennas, means supplying energy from said phase ceived impulse energy. ing means for receiving impulse energy, ñlter means responsive to received impulse energy for delay means to the other of said antennas, re ceiver means including iilter means responsive to energy from each of said antennas, said filter means singling out a frequency which is an odd singling out individual odd-multiple frequencies multiple of the impulsing frequency, and indicat 4. In a course beacon system, a receiver includ of the period of said impulse energy, and indi cating means responsive to two of said odd-mul ing means responsive to the magnitude of said 75 odd-multiple frequency energy. 2,407,287 11 12 provide impulses of a time spaced relation from said ñrst and said second points to provide a course indication, and adjusting the amount of tion from a íirst antenna and a second antenna delay to obtain the time spaced relation from having a predetermined ñxed spaced relationship with respect to said course line, which comprises Cal the impulses required for course indication along a selected one of said radial directions. generating energy in a periodically recurring 12. A method of providing a beacon guiding indication along a desired course line by radia series of relatively short impulses, radiating said 14. In a beacon system for producing a course energy from said íirst antenna over an area in line by impulses of a predetermined time spaced cluding the course line and said second antenna, receiving the radiated energy at a point near said relation according to a selected one of a plurality of radial directions from a given radial center, a ñrst antenna and a second antenna arranged in second antenna, delaying the received energy, radiating the delayed energy from said second a predetermined ñxed spaced relation with respect antenna over an area including said course line, to said radial center, impulse generator means, the delay being such as to produce a predeter ñrst transmitter means for supplying energy from mined time spaced relation between the impulses 15 said generator means to said Iirst antenna for of the energy radiated from said ñrst antenna and said second antenna along said course line, receiving the transmitted pulse energy from both radiation of impulses over a given area covering distances considerably greater than the spacing between said first and second antennas, receiver means for receiving impulse energy from said said first antenna and said second antenna at a point within the radiation area of the tWo an-- 20 ñrst antenna, delay means connected to said re tennas, and determining the position of said point ceiver means, a second transmitter means con relative to said course line by the difference in nected between said delay means and said second antenna for transmission of impulse energy from the time spaced relation of the received impulse said receiver over an area overlapping said given energy from said predetermined time spaced rela tion. 25 area, said delay means being adjustable to deter mine the time spaced relation between the im 13. In a beacon system, the method of produc pulses radiated from said ñrst antenna and said ing a course line identiñed by impulses of a pre second antenna, whereby said impulses indicate determined time spaced relation according to a selected one of a plurality of radial directions for a given delay adjustment a selected course from a given radial center, comprising generating 30 line in a radial direction with respect to said radial center, receiver means for receiving im energy in a periodically recurring series of rela pulse energy from said first and said second an tively short impulses, radiating said energy over tennas, means in said receiver for determining the a given area from a ñrst point spaced a predeter time spaced relation of impulse energy received, mined distance from said radial center, receivingr the radiated energy at a second point spaced from 35 and means responsive to the time spaced rela- . tion of the received impulse energy for indicating said radial center and diametrically disposed with the relative position of said receiver means with respect to said ñrst point, delaying the received respect to said selected course line. energy, radiating the delayed energy from said second point over the area including the area covered by the radiation from said ñrst point to 40 EMILE LABIN.